1,721,390 research outputs found
Denoising Based on Noise Parameter Estimation in Speckled OCT Images Using Neural Network
No full textThis paper presents a neural network based technique to denoise speckled images in optical coherence tomography (OCT). Speckle noise is modeled as Rayleigh distribution, and the neural network estimates the noise parameter, sigma. Twenty features from each image are used as input for training the neural network, and the sigma value is the single output of the network. The certainty of the trained network was more than 91 percent. The promising image results were assessed with three No-Reference metrics, with the Signal-to-Noise ratio of the denoised image being considerably increased
Complementarity of OCT and radiography for imaging investigations in dentistry
Full text linkThere are numerous dental conditions that can appear in the human mouth, from bone diseases like periodontitis or bone loss produced by a massive infection, to common issues like dental cavities. We explored the possible range of dental (and associated bone) conditions using Optical Coherence Tomography (OCT) versus the gold standard of radiological investigations [Erdelyi R.A., Duma V.-F., et al, Materials 13, 4825, 2020]. Clinical and imaging investigations have been performed on real-life patients. Advantages and limitations of using these two imaging techniques were deduced, based on the fact that OCT has better resolution than radiographs (2 to 10 μm versus 75 to 150 μm, respectively), while radiography can perform a complete image of the entire mouth, in contrast to OCT, which has a limited penetration, of only 1 to 2 mm in tooth or soft tissue. The analyses of a range of dental conditions with both techniques clarified when it is better to choose a specific method: (i) for bone diseases, radiographs are more appropriate because they provide images of the entire mouth in one exposure and 3D images of dental conditions; (ii) OCT can spot small cavities in early stages, while radiographs cannot; (iii) measurements performed on cavities spotted with both imaging techniques proved that OCT can provide accurate dimensions, with high contrast and contrast-to-noise ratio. Thus, a classification of each of the two types of imaging techniques for each possible dental condition was obtained. A complementarity of OCT and radiography for investigations in dentistry was concluded
Superpixel guided active contour segmentation of retinal layers in OCT volumes
Full text linkRetinal OCT image segmentation is a precursor to subsequent medical diagnosis by a clinician or machine learning algorithm. In the last decade, many algorithms have been proposed to detect retinal layer boundaries and simplify the image representation. Inspired by the recent success of superpixel methods for pre-processing natural images, we present a novel framework for segmentation of retinal layers in OCT volume data. In our framework, the region of interest (e.g. the fovea) is located using an adaptive-curve method. The cell layer boundaries are then robustly detected firstly using 1D superpixels, applied to A-scans, and then fitting active contours in B-scan images. Thereafter the 3D cell layer surfaces are efficiently segmented from the volume data. The framework was tested on healthy eye data and we show that it is capable of segmenting up to 12 layers. The experimental results imply the effectiveness of proposed method and indicate its robustness to low image resolution and intrinsic speckle noise
Roughness measurements using optical coherence tomography: a preliminary study
Full text linkTo determine the roughness is an important aspect in both industrial and biomedical applications. We propose and utilize for roughness evaluations, a non-destructive evaluation methods, Optical Coherence Tomography (OCT). For the metallic surfaces investigated from this point of view, the Ra and Rz parameters are utilized, according to ISO 4287/1988. Also, according to ISO 4280 and ISO 3274 standards, the measurements have been made on 12.5 mm portions. In order to accommodate such evaluations with the specific OCT field-of-view, four consecutive OCT images have been made for each sample, and an appropriate processing of the data collected from the surface profiles has been made. A validation of the results obtained with OCT has been completed with the gold standard for such evaluations, using a contact mechanical method, with a Mitutuyo profiler
Modern evaluation of the quality of the techniques of root canal dental obturation
Full text linkBackground: One of the key factors for a successful endodontic therapy is to adequately fill the root canals. The aim of this in vitro study was to compare the quality of three different techniques of root canal obturation: tapered singlecone, cold lateral condensation, warm vertical condensation and injection system, using non-invasive Optical Coherence Tomography (OCT).
Materials and methods: A total of 30 extracted single-rooted teeth, prepared with Reciproc System (VDW, silver Reciproc ) were divided into three groups, based on the filling method: the first group obturated with “single-cone” (n=10) Reciproc guttapercha single-cone tapered according to the diameter, length and conicity of the preparation, the second group obturated with cold lateral condensation (n=10) and the third group, “combined-system” (E&Q META BIOMED) (n=10). OCT technology can generate high-resolution cross-sectional imaging, capable to evaluate the micro-leakages of dental restorations and endodontic fillings.
Results: OCT showed that none of the root canal filled teeth were gape-free; the highest percentage of filling material was observed in the combined system group (warm vertical and injection system).
Conclusions: OCT represents a valuable method for investigation with high depth resolution which can be used for evaluation of endodontic fillings
Optoelectronic evaluation of indirect dental veneers interfaces
Full text linkDental indirect veneers have become the most functional and cost-effective method for providing high-aesthetic results whenever smile design enhancement is required. Yet, clinical failures have been reported due to the detachment of the veneers from the dental hard tissues, as well as to chipping and microleakage. Many experimental studies have been conducted in order to identify clinical and technical solutions for enhancing the adhesive and biomechanical properties of the veneers, by promoting the same classical, linear marginal contour of these particular indirect restorations. Thus, the aim of this study is to develop a novel design of the veneers deemed to augment the interfacial adhesive forces and, furthermore, to investigate the bonded interfaces by using optical coherence tomography
Biomimetic Tizian 'table tops' analyzed with swept source optical coherence tomography
Full text link"Table tops"/occlusal veneers are partial crowns that allow for the biomimetic restoration of worn teeth in bruxing patients. The biomimetic approach includes a CAD/CAM composite resin for the manufacturing of the "table tops", for example Tizian, which is a zirconia reinforced composite (Schutz Dental Group). In the present study we prove the value of a fast swept source optical coherence tomography (SS-OCT) system in the evaluation of the marginal fit of Tizian "table tops". 12 maxillary first premolars were extracted and minimally invasive prepared for "table tops". The Tizian "table tops" were then adhesively cemented on the natural teeth with Variolink II (Ivoclar Vivadent). A SS-OCT system has been used to evaluate the marginal and internal adaptation of Tizian "table tops". The SS (Axsun Technologies, Billerica, MA) has a central wavelength of 1060 nm, a sweeping range 106 nm (quoted at 10 dB), and a 100 kHz line rate. The depth resolution of the system, measured experimentally in air was 10 ?m. The same samples were analyzed by using a micro-computed tomography (?CT) system, in order cu confirm the data obtained by using OCT. The imaging system used for this study offers good spatial resolutions in both directions, transversal and longitudinal, of around 10 ?m, a high sensitivity, and it is also able to acquire entire 3D volumes as fast as 2.5 s. Once the full dataset has been acquired, rendered high resolutions en-face projections could be produced. With it, the "table top" – cement – abutment tooth interfaces were observed on both C-scans as 2D images and also in the 3D reconstructions; the system was able to detect several open interfaces, which were confirmed on the ?CT i mages. The SS-OCT system allows for an efficient evaluation of biomimetic Tizian "table tops"
Fourier Domain Optical Coherence Tomography, a structural and a functional imaging modality
Full text linkMarginal integrity evaluation of dental composite using optical coherence tomography
No full textIn clinical dental practice it is often difficult or even impossible to distinguish and control interfacial adhesive defects from adhesive restorations using visual inspection or other traditional diagnostic methods. Nonetheless, non-invasive biomedical imaging methods like Optical Coherence Tomography (OCT) may provide a better view in this diagnostic outline. The aim of this study is to explore evaluations of the marginal adaptation of class I resin composites restorations using Time Domain (TD) OCT. Posterior human teeth have been chosen for this study. The teeth were stored in 0.9% physiological saline solution prior to use. A classical round-shaped class I cavity was prepared and cavities were restored with Charisma Diamond composite by Heraeus Kulzer and using a system of etch and rinse boding. The specimens were subjected to water storage and then to thermo-cycling. Three dimensional (3-D) scans of the restoration were obtained using a TD-OCT system centered at a 1300 nm wavelength. Open marginal adaptation at the interfaces and gaps inside the composite resins materials were identified using the proposed method. In conclusion, OCT has numerous advantages which justify its use for in vitro, as well as for in vivo studies. It can therefore be considered for non-invasive and fast detection of gaps at the restoration interface
Advanced systems and methods for collecting accurate data in optical coherence tomography
Full text linkOptical coherence tomography (OCT) has recently emerged as a valuable technique in biomedical research and medical diagnostics. OCT based instruments allow acquisi- tion of high-resolution information about the internal structure of translucent organs and tissues without damaging the object. However, unaccounted object movements reduce the quality of acquired data, particularly in functional imaging and in OCT modalities that rely on continuous monitoring. Therefore there is a need for methods that allow mitigating the negative effects of the object movements on the data quality.In this thesis we present several methods and devices that allow improving the ac- curacy of collected data. First we introduce a novel frequency multiplexing method for OCT, which enables simultaneous measurements using several frequency-encoded channels. By doing so, several parameters are measured in the same time, reducing the time to acquire the data and making the technology less sensitive to object movements. We employed the method to extend the functionality of several OCT modalities. We have applied the multiplexer to enable simultaneous en face time domain OCT imag- ing at different depths. We have demonstrated a polarisation sensitive OCT set-up where different multiplexer channels are employed to perform polarisation sensitive measurements.Furthermore, we have demonstrated how the multiplexer can be applied to extend the sensitivity range in swept source based OCT systems. The experiments presented in this thesis illustrate the flexibility of our new multiplexing method, which has proven useful not only for increasing the accuracy of collected data, but as well for increasing the efficiency in using the light from the object.Alternatively, we have investigated tracking as a way to improve the quality of the OCT data acquired from the moving targets. We have demonstrated a closed-loop tracking based set-up that uses low coherence interferometry to continuously monitor the cardiac dynamics of a Drosophila melanogaster embryo
- …
